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package javax.naming.spi;

import javax.naming.*;
import javax.naming.directory.Attributes;
import java.util.Hashtable;

/**
 * This interface represents a factory for obtaining the state of an
 * object and corresponding attributes for binding.
 * <p>
 * The JNDI framework allows for object implementations to
 * be loaded in dynamically via <tt>object factories</tt>.
 * <p>
 * A <tt>DirStateFactory</tt> extends <tt>StateFactory</tt>
 * by allowing an <tt>Attributes</tt> instance
 * to be supplied to and be returned by the <tt>getStateToBind()</tt> method.
 * <tt>DirStateFactory</tt> implementations are intended to be used by
 * <tt>DirContext</tt> service providers.
 * When a caller binds an object using <tt>DirContext.bind()</tt>,
 * he might also specify a set of attributes to be bound with the object.
 * The object and attributes to be bound are passed to
 * the <tt>getStateToBind()</tt> method of a factory.
 * If the factory processes the object and attributes, it returns
 * a corresponding pair of object and attributes to be bound.
 * If the factory does not process the object, it must return null.
 * <p>
 * For example, a caller might bind a printer object with some printer-related
 * attributes.
 * <blockquote><pre>
 * ctx.rebind("inky", printer, printerAttrs);
 * </pre></blockquote>
 * An LDAP service provider for <tt>ctx</tt> uses a <tt>DirStateFactory</tt>
 * (indirectly via <tt>DirectoryManager.getStateToBind()</tt>)
 * and gives it <tt>printer</tt> and <tt>printerAttrs</tt>. A factory for
 * an LDAP directory might turn <tt>printer</tt> into a set of attributes
 * and merge that with <tt>printerAttrs</tt>. The service provider then
 * uses the resulting attributes to create an LDAP entry and updates
 * the directory.
 *
 * <p> Since <tt>DirStateFactory</tt> extends <tt>StateFactory</tt>, it
 * has two <tt>getStateToBind()</tt> methods, where one
 * differs from the other by the attributes
 * argument. <tt>DirectoryManager.getStateToBind()</tt> will only use
 * the form that accepts the attributes argument, while
 * <tt>NamingManager.getStateToBind()</tt> will only use the form that
 * does not accept the attributes argument.
 *
 * <p> Either form of the <tt>getStateToBind()</tt> method of a
 * DirStateFactory may be invoked multiple times, possibly using different
 * parameters.  The implementation is thread-safe.
 *
 * @author Rosanna Lee
 * @author Scott Seligman
 * @see DirectoryManager#getStateToBind
 * @see DirObjectFactory
 * @since 1.3
 */
public interface DirStateFactory extends StateFactory {

  /**
   * Retrieves the state of an object for binding given the object and attributes
   * to be transformed.
   * <p>
   * <tt>DirectoryManager.getStateToBind()</tt>
   * successively loads in state factories. If a factory implements
   * <tt>DirStateFactory</tt>, <tt>DirectoryManager</tt> invokes this method;
   * otherwise, it invokes <tt>StateFactory.getStateToBind()</tt>.
   * It does this until a factory produces a non-null answer.
   * <p>
   * When an exception is thrown by a factory,
   * the exception is passed on to the caller
   * of <tt>DirectoryManager.getStateToBind()</tt>. The search for other factories
   * that may produce a non-null answer is halted.
   * A factory should only throw an exception if it is sure that
   * it is the only intended factory and that no other factories
   * should be tried.
   * If this factory cannot create an object using the arguments supplied,
   * it should return null.
   * <p>
   * The <code>name</code> and <code>nameCtx</code> parameters may
   * optionally be used to specify the name of the object being created.
   * See the description of "Name and Context Parameters" in
   * {@link ObjectFactory#getObjectInstance ObjectFactory.getObjectInstance()}
   * for details.
   * If a factory uses <code>nameCtx</code> it should synchronize its use
   * against concurrent access, since context implementations are not
   * guaranteed to be thread-safe.
   * <p>
   * The <tt>name</tt>, <tt>inAttrs</tt>, and <tt>environment</tt> parameters
   * are owned by the caller.
   * The implementation will not modify these objects or keep references
   * to them, although it may keep references to clones or copies.
   * The object returned by this method is owned by the caller.
   * The implementation will not subsequently modify it.
   * It will contain either a new <tt>Attributes</tt> object that is
   * likewise owned by the caller, or a reference to the original
   * <tt>inAttrs</tt> parameter.
   *
   * @param obj A possibly null object whose state is to be retrieved.
   * @param name The name of this object relative to <code>nameCtx</code>, or null if no name is
   * specified.
   * @param nameCtx The context relative to which the <code>name</code> parameter is specified, or
   * null if <code>name</code> is relative to the default initial context.
   * @param environment The possibly null environment to be used in the creation of the object's
   * state.
   * @param inAttrs The possibly null attributes to be bound with the object. The factory must not
   * modify <tt>inAttrs</tt>.
   * @return A <tt>Result</tt> containing the object's state for binding and the corresponding
   * attributes to be bound; null if the object don't use this factory.
   * @throws NamingException If this factory encountered an exception while attempting to get the
   * object's state, and no other factories are to be tried.
   * @see DirectoryManager#getStateToBind
   */
  public Result getStateToBind(Object obj, Name name, Context nameCtx,
      Hashtable<?, ?> environment,
      Attributes inAttrs)
      throws NamingException;


  /**
   * An object/attributes pair for returning the result of
   * DirStateFactory.getStateToBind().
   */
  public static class Result {

    /**
     * The possibly null object to be bound.
     */
    private Object obj;


    /**
     * The possibly null attributes to be bound.
     */
    private Attributes attrs;

    /**
     * Constructs an instance of Result.
     *
     * @param obj The possibly null object to be bound.
     * @param outAttrs The possibly null attributes to be bound.
     */
    public Result(Object obj, Attributes outAttrs) {
      this.obj = obj;
      this.attrs = outAttrs;
    }

    /**
     * Retrieves the object to be bound.
     *
     * @return The possibly null object to be bound.
     */
    public Object getObject() {
      return obj;
    }

    ;

    /**
     * Retrieves the attributes to be bound.
     *
     * @return The possibly null attributes to be bound.
     */
    public Attributes getAttributes() {
      return attrs;
    }

    ;

  }
}
